Passive Planar Microwave Devices

The aim of this book is to highlight some recent advances in microwave planar devices. The development of planar technologies still generates great interest because of their many applications in fields as diverse as wireless communications, medical instrumentation, remote sensing, etc. In this book, particular interest has been focused on an electronically controllable phase shifter, wireless sensing, a multiband textile antenna, a MIMO antenna in microstrip technology, a miniaturized spoof plasmonic antipodal Vivaldi antenna, a dual-band balanced bandpass filter, glide-symmetric structures, a transparent multiband antenna for vehicle communications, a multilayer bandpass filter with high selectivity, microwave planar cutoff probes, and a wideband transition from microstrip to ridge empty substrate integrated waveguide

Compact Microwave Dual-band Bandpass Filter Design

The modern wireless communication systems require dual-band bandpass filters to support the standards that work at multiple frequency bands. This thesis demonstrates two design approaches for the development of compact microwave dual-band bandpass filters. The first approach is based on synthesising a dual-passband filter response utilising only one resonant frequency of the resonators. The second approach employs dual-band resonators that have tuneable the first and the second resonant frequencies to form the dual-passbands filter response. The dual-passband response synthesis method synthesises a response with dual passbands that is generated by a frequency transformation that places a finite frequency zero within the single- passband of a filter to split it into dual passbands. The transformed dual-passband response is characterised by the synthesised coupling matrix that consists of the coupling coefficients between coupled resonators. Two filters have been designed and fabricated using microstrip square open-loop and TE01δ mode quarter cylindrical dielectric resonators. The investigation based on simulation studies and measured results revealed that unloaded quality factor of the resonator is required to be ten times greater than the quality factor of each passband in order to realise the narrow passbands. The dual-band resonator methods employ multiple resonant modes of the resonator operating at different frequencies to implement the multiple passbands, respectively. Stepped impedance resonators in stripline and coaxial configurations have been presented and analysed for the realisation of dual-band bandpass filters. A second order dual-band bandpass filter formed by coaxial stepped impedance resonators has been designed, fabricated and tested. The measured frequency response agree well with the simulated response. The estimated breakdown power shows that the filter is capable of high power applications. Non-uniform pitch helical resonators are also proposed for the implementation of dual-band bandpass filters. Two non-uniform pitch helical resonator structures have been analytically modelled. The theoretical models of the non- uniform pitch helical resonators have been developed for accurate prediction of its dual-band characteristics. It is also employed in the general design process of the non-uniform pitch helical resonators. Resonator examples have been presented to show the applicability and validity of the analysis and simulation. Three dual-band bandpass filters have been designed and implemented using non-uniform pitch helical resonators. Their measured frequency responses agree reasonably with the ideal responses. Additionally, the simulation shows that the designed dual-band bandpass filters have relatively high power handling capability

Analysis and Design of Low-Cost Waveguide Filters for Wireless Communications

The area of research of this thesis is built around advanced waveguide filter structures. Waveguide filters and the waveguide technology in general are renowned for high power capacity, low losses and excellent electromagnetic shielding. Waveguide filters are important components in fixed wireless communications as well as in satellite and radar systems. Furthermore, their advantages and utilization become even greater with increase in frequency, which is a trend in modern communication systems because upper frequency bands offer larger channel capacities. However, waveguide filters are relatively bulky and expensive. To comply with more and more demanding miniaturization and cost-cutting requirements, compactness and economical design represent some of the main contemporary focuses of interest. Approaches that are used to achieve this include use of planar inserts to build waveguide discontinuities, additive manufacturing and substrate integration. At the same time, waveguide filters still need to satisfy opposed stringent requirements like small insertion loss, high selectivity and multiband operation. Another difficulty that metal waveguide components face is integration with other circuitry, especially important when solid-state active devices are included. Thus, improvements of interconnections between waveguide and other transmission interfaces are addressed too. The thesis elaborates the following aspects of work: Further analysis and improved explanations regarding advanced waveguide filters with E-plane inserts developed by the Wireless Communications Research Group, using both cross coupled resonators and extracted pole sections (Experiments with higher filter orders, use of tuning screws, degrees of freedom in design, etc. Thorough performance comparison with competing filter technologies) - Proposing novel E-plane filter sections with I-shaped insets - Extension of the E-plane filtering structures with metal fins to new compact dual band filters with high frequency selectivity and miniaturized diplexers. - Introduction of easy-to-build waveguide filters with polymer insert frames and high-performance low-profile cavity filters, taking advantage of enhanced fabrication capabilities when using additive manufacturing - Developing new substrate integrated filters, as well as circuits used to transfer signals between different interfaces Namely, these are substrate integrated waveguide to metal waveguide planar transitions that do not require any modifications of the metal waveguides. Such novel transitions have been designed both for single and orthogonal signal polarizations

Antennas and Propagation

This Special Issue gathers topics of utmost interest in the field of antennas and propagation, such as: new directions and challenges in antenna design and propagation; innovative antenna technologies for space applications; metamaterial, metasurface and other periodic structures; antennas for 5G; electromagnetic field measurements and remote sensing applications

Reconfigurable Antennas

In this new book, we present a collection of the advanced developments in reconfigurable antennas and metasurfaces. It begins with a review of reconfigurability technologies, and proceeds to the presentation of a series of reconfigurable antennas, UWB MIMO antennas and reconfigurable arrays. Then, reconfigurable metasurfaces are introduced and the latest advances are presented and discussed